Glucocorticoid steroid hormones are routinely used in the treatment of steroid-responsive leukemia, such as T-cell acute lymphoblastic leukemia (ALL), multiple myeloma, and others. They are effective by triggering apoptosis (programmed cell death) in sensitive lymphoblasts. Successful therapy requires functional human glucocorticoid receptor (hGR), an intracellular protein that is a member of the nuclear steroid hormone receptor super-family. A critical step in the steroid pathway is the ligand-induced auto-up-regulation of the hGR itself. Our laboratory has discovered a new hGR promoter, termed 1A, which contains hormone- responsive sequences that mediate steroid stimulation of hGR gene transcription and protein expression. The central hypothesis of this proposal is that the regulation of transcription of the human glucocorticoid receptor (hGR) gene promoter causes alterations in the quantity of the hGR protein, and that this affects the sensitivity of the cell to the steroid hormone and the responsiveness of T-cell acute lymphoblastic leukemia (ALL) blasts to steroid therapy. The first specific aim is to elucidate the molecular mechanism of hGR stimulation of its own 1A promoter by determining the role of c-Myb and members of the c-Ets family of transcription factors (PU.1, Spi-B). The molecular mechanism(s)that distinguishes auto-up- and down- regulation of the hGR by hormone will be determined, and the role of the c-Myb and c-Ets proteins in causing hormone-mediated apoptosis in T-cell ALL will be assessed. The second specific aim will elucidate the molecular mechanism(s) by identifying the coregulators that contribute to both the auto-up-regulation and auto-down-regulation of hGR 1A promoter activity.. The third specific aim will assay the levels of hGR transcripts in samples from leukemia patients. A sensitive, ex vivo, hormone-challenge, RT-PCR assay will be developed in attempts to stratify leukemia patients into responders and resistant populations. This multifaceted translational approach will lead to an improved diagnosis and treatment of leukemia and a more rational approach to steroid therapy.